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Sunday, January 4, 2015

In this morning’s Sunday Independent magazine (Sunday,
January 4th), there is a half page article entitled “Supercharge
your diet” by Dr Johnny Bowden, described in the article as a weight-loss
expert. I have picked out a few of his statements to comment on.

Under the heading “Protein planning”, he makes the following
statement: “Many protein-rich foods – tuna, avocado, chicken- also contain the
amino acid tyrosine, which leaves you feeling wide awake”. Now if you consult
the USDA Food Composition Tables[1]
and specifically search for tyrosine, you find that all foods that contain
protein must contain tyrosine. Quite simply, proteins may vary in their level
of tyrosine, but if it’s a protein, it has to have the amino acid tyrosine. Its
actually hard to understand why these three foods were mentioned. For example,
both cod and shellfish have more tyrosine than tuna and turkey has more
tyrosine than chicken. So, if you buy into the idea that tyrosine “leaves you
feeling wide awake” then any protein rich food will suffice. Now it’s worth
delving into the literature to see what the true science oracle has to say
about tyrosine and alertness. One study deprived subjects of sleep and
subjected them to a battery of mental tests on the night the study began[2].
They would remain awake for 24 hours in total. Half were given a placebo
(starch) and the other half was given tyrosine at the level of 0.15g per kg of
body weight. Tyrosine improved alertness in these sleep-deprived subjects,
which lasted about 3 hours. So, if you are sleep deprived for 24 hours and want
to get the three hour boost from tyrosine, the equivalent dose of roasted
chicken (meat only) is about 10 servings a day, each weighing 140 g. That is
1.4 kg of roast chicken and that accounts for nearly 2,400 calories. It sort of
reminds me of Cool Hand Luke!

Moving on, Dr Johnny also advocates that we “Cut the carbs”.
He writes thus: “Halving your carbohydrate intake will increase your vitality
and energy…Carbs cause a rapid rise and fall in blood glucose, resulting in a
‘crashed’ feeling of lethargy and fatigue”. In another section entitled “Get
off sugar” he writes: “The number-one drainer of energy is sugar”. I am in
nutrition a long time and the concept of a “drain” is one I’m not familiar with
so I can’t comment or explain on what exactly this “drain” is. So let’s think
about carbs and vitality. The average person apportions their caloric
expenditure as follows: 70% as basal metabolic rate accounting for the
functioning of essential organs such as the heart, lungs, liver, spleen, bone
marrow, brain, gut etc.; 20% as physical activity; 10% as the thermic effect of
food, that is, the cost of digestion, absorption and distribution of the
components of a meal. The brain alone accounts for about 20% of total daily
energy use (its as high as 75% in newborns). So which tires us most, the brain
or physical activity, both of which account for 20% of daily caloric intake?
Now the brain is an obligate glucose consumer so it will only ever use glucose
in the course of a normal day and it consumes a staggering 6 grams of glucose
per hour, equivalent to 144 g/d[3].
Our National Nutrition surveys here in Ireland show that we eat 230 g/d of
carbohydrate so halving that would lead to an intake of 115g/d which is only
about 80% of our brain needs[4].
So my frank view of halving carbohydrate intake is that it would quite likely
lead to lethargy than vitality.

Finally, I’d like to comment on the section entitled “Raw
materials”. Here, Dr Johnny states that: “A lot of beneficial nutrients and
enzymes found in raw foods are destroyed by high heat”. Yes, there are enzymes
in plant and animal foods and because all, and I mean all enzymes are proteins, the relevant enzymes in plant and animal
foods were synthesised in those foods according to the genetic code of the relevant
animal or plant. These genetic codes are very different from ours and, if whole
proteins that are not synthesised according to our genetic code cross our
gut barrier and enter our blood
system, we get an immune reaction. The immune reaction might go unnoticed or it
might induce an allergy all the way up to a life threatening anaphylactic
reaction. Just to be sure that this doesn’t happen we have our own enzymes in
the gut, which break down the plant and animal food enzymes into their
constituent amino acids. We absorb these and then re-assemble them according to
our genetic code.So, dear readers, the
last thing you want to encounter is the absorption intact of animal and plant
food proteins. This warning does not apply to cannibals by the way since they
ingest their own species. Enough January nutrition non-sense!

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"Ever seen a fat fox ~ Human obesity explored"

About Me

I graduated from University College Dublin in 1971 with an Masters in Agricultural Chemistry, took a PhD at Sydney University in 1976 and joined the University of Southampton Medical School as a lecturer in human nutrition in 1977. In 1984 I returned to Ireland to take up a post at the Department of Clinical Medicine Trinity College Dublin and was appointed as professor of human nutrition. In 2006 I left Trinity and moved to University College Dublin as Director of the UCD Institute of Food and Health. I am a former President of the Nutrition Society and I've served on several EU and UN committees on nutrition and Health. I have published over 350+ peer reviewed scientific papers in Public Health Nutrition and Molecular Nutrition and am principal investigator on several national and EU projects (www.ucd.ie/jingo; www.food4me.org). My popular books are "Something to chew on ~ challenging controversies in human nutrition" and "Ever seen a fat fox: human obesity explored"